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Modify property of object in List [Answered]

BBujju10/14/2022
I have a struct like this:

public struct MyStruct
{
    public ulong Id { get; set; }

    public string MyProperty { get; set; }
}

And I have a List<MyStruct>. I want to modify MyProperty for a certain MyStruct in the list, using the Id property. I tried this:

MyList.Where(x => x.Id == id).ToList().ForEach(x => x.MyProperty = myVariable);

But it didn't work.
TTheBoxyBear10/14/2022
MyStruct is a struct so you can't change the value of properties
TTheBoxyBear10/14/2022
Loop or not
TTheBoxyBear10/14/2022
Ir you need to edit the properties, make it a class to make it a reference type
TTheBoxyBear10/14/2022
$ref
MMODiX10/14/2022
https://cdn.discordapp.com/attachments/364492811489509376/692833980650881084/pass-by-reference-vs-pass-by-value-animation.gif
Mmtreit10/14/2022
Yes, use a class if you want mutable properties. In general structs should be immutable.
Mmtreit10/14/2022
Now, knowing that a struct is passed by value (meaning a copy is made when you access it), you COULD achieve what you want even using structs - by mutating the copy and then putting that copy back into the list.
Mmtreit10/14/2022
List<MyStruct> data = new();

for (int i = 0; i < 10; i++)
{
    data.Add(new MyStruct { Id = (ulong)i, MyProperty = i.ToString() });
}

for (int i = 0; i < data.Count; i++)
{
    var item = data[i];
    item.MyProperty = item.MyProperty + " MODIFIED!";
    data[i] = item;
}

foreach (var item in data)
{
    Console.WriteLine(item.MyProperty);
}
Mmtreit10/14/2022
However, this is doing a bunch of extra work for no good reason - just use a class instead.
Mmtreit10/14/2022
You could also achieve this with ref locals if the data was an array instead of a list. Again though, I would just use a class or a record.
BBujju10/14/2022
Thanks
AAccord10/14/2022
✅ This post has been marked as answered!